SN 2002ap

A. Gal-Yam, E. O. Ofek, O. Shemmer
report:

Using the Wise Observatory 1m telescope we have obtained UBVRI
photometry of SN 2002ap during February 2002. Using our most conservative 
estimate for the date of the $B-$band peak, 
Feb. $7.1_{-1.3}^{+7.6}$ days, and assuming that the lag between a
hypothetical GRB (that might have been associated with this SN) and the time
of $B-$band maximum is similar to that measured for SN 1998bw (14.3 days,
Galama et al. 1998), we would expect the GRB trigger to have occurred around
Jan. $23.8_{-1.3}^{+7.6}$ days. 
However, if we use instead our estimated $U-$band peak date, 
Feb. $4.7_{-1.9}^{+1.1}$ days, which is best constrained by our photometry, 
along with the appropriate $U-$band time lag from Galama et al. 1998 
(13.7 days), the resulting GRB trigger time is Jan. $22.0_{-1.9}^{+1.1}$ 
days. Hurley et al. (GCN 1252
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 ) found no candidate GRB that might be 
associated with SN 2002ap in an intensive search of gamma-ray data from 
the IPN, starting Jan. 21. Our results suggest that 
the GRB trigger may have occurred outside the time frame searched. 
If the GRB-peak magnitude time lag for SN 2002ap was just one day longer
than the lag measured for SN 1998bw, the trigger is likely to have been
missed by Hurley et al. We conclude that in order to detect, or set a secure
upper limit to the fluence of a GRB associated with SN 2002ap, a search similar
to the one reported by Hurley et al. should be extended to include data
taken several days prior to January 21.   

This message may be cited.

K. Hurley, on behalf of the Ulysses GRB team;

E. Mazets, S. Golenetskii, on behalf of the Konus-Wind GRB team;

C. Guidorzi, E. Montanari, F. Frontera, and M. Feroci, on behalf of the
BeppoSAX GRBM team;

G. Ricker, D. Lamb, S. Woosley, G. Crew, J. Doty, G.  Monnelly, J.
Villasenor, N.  Butler, J.G. Jernigan, A. Levine, F.  Martel, E.
Morgan, G.  Prigozhin, J. Braga, R. Manchanda, G.  Pizzichini, N.
Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, K. Torii, T.  Sakamoto,
A. Yoshida, E. Fenimore, M. Galassi, T. Donaghy, C.  Graziani, T.
Tavenner, J-L Atteia, M. Boer, J-F Olive, and J-P Dezalay, on behalf of
the HETE Team;

I.Mitrofanov, D.Anfimov and M.Litvak on behalf on HEND/Odyssey GRB
team;

W. Boynton, C. Fellows, K. Harshman, and C. Shinohara, on
behalf of the GRS/Odyssey GRB team; and

T. Cline, on behalf of the Ulysses, Konus, and HETE GRB teams, report:

We have searched for a gamma ray burst that might be associated with
SN2002ap (Nakano, IAUC 7810), to investigate its similarity to the
hypernova SN1998bw (Meikle et al. IAUC 7811).  We have limited our
search to data obtained between January 21 and January 29, 2002.
During that period, no burst which could be localized by the IPN was
found to have a source position in any way consistent with that of the
supernova.  That is, there was no event observed with two or more
spacecraft that produced a source annulus or error box consistent with
the supernova, and, although several events were observed each by
single spacecraft in the network during this time, none of these
unconfirmed events could be localized with any precision.  Thus,
lacking any definite evidence for an association, we quote only upper
limits to a GRB from the direction of SN2002ap. These upper limits
depend on the duration, spectrum, and arrival time within the search
window, all of which are unknown.

Each instrument in the network has a different sensitivity and duty
cycle (determined by, among other things, the periods for which data
were recovered, Earth-occultation for those spacecraft in low Earth
orbit, Mars-occultation for the Mars Odyssey spacecraft, and the angle
which the direction of SN2002ap made with the detector axis).  For
simplicity, we have assumed a 1 s long burst with a typical hard GRB
spectrum to obtain the following fluence upper limits.  We note that
since SN2002ap is about 4 times closer than SN1998bw, then assuming
that GRB980425 indeed originated in SN1998bw, a burst from SN2002ap
might have been at least an order of magnitude more intense (neglecting
beaming), and therefore easily detectable.

1. Ulysses.  Duty cycle 95%.  The Ulysses GRB detector has a
quasi-isotropic response, so the arrival angle makes little
difference.  Upper limit: ~10^-6 erg/cm^2, 25-150 keV.

2. Konus.  Duty cycle ~98%.  The Wind spacecraft is several
light-seconds from Earth, so the source was not occulted.
Konus consists of two uncollimated right circular cylindrical
detectors facing the north and south ecliptic poles.  The ecliptic
latitude of SN2002ap is approximately 5 degrees, so it is seen edge-on
by the detectors.  Upper limit:  5 x 10^-7 erg/cm^2, 20-2000 keV.

3. BeppoSAX GRBM. Complex response pattern and time-dependent
duty cycle. 

Start date	 End date		Duty Cycle	40-700 keV
							fluence, erg/cm^2
------------------------------------------------------------------------
20 Jan 06:32:49	 21 Jan 13:00:00	47%		4 x 10^(-7)

21 Jan 13:00:00  22 Jan 14:41:09	 0% (NO DATA)	--

22 Jan 14:41:09  22 Jan 20:00:58	36%		1 x 10^(-7)

22 Jan 20:00:58  24 Jan 17:00:00	 0% (NO DATA)	--

24 Jan 17:00:00	 25 Jan 09:35:00	42%		4 x 10^(-7)
 
25 Jan 09:35:00  29 Jan 23:59:59	 0% (NO DATA)	--
------------------------------------------------------------------------

4. HETE-FREGATE.  Duty cycle 22%.  The FREGATE instrument consists of
four collimated right circular cylindrical detectors facing the
anti-solar direction.  SN2002ap made an angle of ~96 degrees to the
detector axis, so any burst from it would not only have been observed
edge-on, but also through the collimator.   It would not have been
observed by the WXM or the SXC.  Nevertheless, bursts have been
detected by FREGATE under precisely these non-ideal conditions.
Sensitivity: 3.2 x 10^-6 erg/cm^2, 250-400 keV.  The high energy
range is due to the fact that the burst would have had to traverse
the collimator.

5. Mars Odyssey HEND experiment.  Duty cycle 64%.  Sensitivity
10^-6 erg/cm^2 >60 keV.

Many of these numbers are preliminary, and depend strongly on the
assumptions about the time history, duration, arrival time, and
spectrum of the assumed burst.  More detailed information may be
obtained from the people directly responsible for each experiment in
the network.

Sylvio Klose, Eike Guenther, and Jens Woitas 
       (Thueringer Landessternwarte Tautenburg)

report:


High-resolution spectra of SN 2002ap were aquired using the
Echelle-spectrograph at the Tautenburg 2-m telescope on February 2.8 UT 
and 3.8 UT. The detector is a 2k x 2k CCD chip with 15 micron
pixels. The spectral resolution was R = 70 000 (0.04 Angstrom per
pixel; slit 1.04 arcsec). At the time of the observations SN 2002ap
was at an apparent magnitude of about V=12. The spectra were
reduced in a standard fashion. Wavelength calibration was performed
by means of ThAr lamps. The signal-to-noise ratio of the combined
images is about 30. This is sufficiently high to check the spectrum
for lines from the interstellar medium in the supernova host galaxy
(M 74).

In the combined spectra we detect an absorption feature at a
heliocentric velocity of (660 +/- 2) km/s what we attribute to
redshifted NaI D1 at the velocity of the host [1, 2]. For the D1
component we measure an equivalent width of (30 +/- 5) milli-Angstrom,
whereas the redshifted D2 component is blended with a telluric line.
Assuming that the empirical relation between the equivalent width of
Na I D1 and interstellar reddening in our Galaxy [3] is also
representative for the interstellar medium in M 74 we arrive at a
reddening in the supernova host of E(B-V) = (0.008 +/- 0.002)
mag. Thus, assuming a ratio of total-to-selective extinction of about
3, our data are in agreement with A_V (host) = (0.025 +/- 0.005)
magnitudes. In other words, at a projected distance of the supernova
of about 13.5 kpc from the center of M 74 (assuming a distance of 10
Mpc, [4]), the supernova light is nearly unaffected by dust in M 74.


References: 

[1] Tormen, G. & Burstein, D.: Astrophys. J. Suppl. Ser. 96 (1995) 123
[2] Smartt, S. & Meikle, P.: IAUC 7822 (2002)
[3] Munari, F. & Zwitter, T.: Astron. Astrophys. 318 (1997) 269
[4] Chen, P. C. et al.: Astrophys. J. 395 (1992) L 41

The supernova spectrum is posted at 
http://www.tls-tautenburg.de/research/klose/SN2002ap.html .

This message may be quoted.

J. T. Lauroesch, D. G. York, C. Hastings, D. V. Bowen, D. Meyer, and
D. Q. Lamb report:

We obtained 75 minutes of integration (five 15-minute exposures) on
SN2002ap using the echelle spectrograph (ARCES) on the Apache Point
Observatory 3.5-meter telescope.  The spectra were taken with a 1.6
arcsecond wide slit, 3.2 arcsec long, in seeing of about 1.5 arcsec.
The spectra give complete spectral coverage from 3600 A to 10500A. The
signal to noise ratio (per pixel) is about 20 at Ca II and 50 at Na I.

These spectra, at a resolution of 8 km/s, show clear detections of
interstellar NaI and CaII in both the Milky Way and M74.  A  weak,
narrow, NaI feature (D1 and D2) is detected in M74 with a column
density of approximately 2.5e11, suggesting there may be little cold
interstellar gas in M74 in front of the SN.  Assuming the "typical"
Galactic relation between NaI and HI, this fact would suggest a total
hydrogen column of approximately 5e19 in M74 along this sightline.  Two
components are seen in M74 in CaII; one narrow, corresponding in
velocity to the NaI absorption noted above, and a second broader
component, approximately +25 km/sec with respect to the Na I feature.
The Ca II features each span roughly 50 km/sec, and are centered near
650 km/sec (heliocentric).  The Galactic Na I and Ca II lines are about
5 times stronger that their M74 counterparts in the SN spectrum.  This
object, while it is still bright, is ideal for measuring interstellar
abundances in the outer part of the M74 galaxy.

This sightline passes near the location of a known Galactic high
velocity H I cloud (Wakker 2001) at approximately -100 km/sec (LSR);
however, no absorption is detected at these velocities in either Ca II
or Na I to limits of 20 and 10 milli-Angstroms respectively.

No other significant narrow absorption or emission lines were seen in
the spectrum.

Further observations are in progress.

P. Vreeswijk (University of Amsterdam) and S. Smartt (Institute of
Astronomy, Cambridge) report that images taken by Gerry Gilmore and
Rosie Wyse on the Isaac Newton Telescope, La Palma on Feb. 2.9 UT have
allowed an accurate projection of the position of SN 2002ap on the
pre-discovery images reported in IAUC 7816. Within the new errors,
the SN is not coincident with the V = 21.2 object reported as a
possible progenitor. The difference in position between SN 2002ap and
this object is 1.7 +/- 0.3" where the error is dominated by the error
in the position of the faint object. There is no object in the pre-
discovery images at the SN position, to limiting magnitudes (5-sigma, 
2" aperture radius) of U = 20.8, B = 22.1, V = 22.0, and I = 20.8.

SUPERNOVA 2002ap IN M74
     L. Wang, Lawrence Berkeley National Laboratory (LBNL);
D. Baade, European Southern Observatory (ESO); C. Fransson,
Stockholm Observatory; P. Hoeflich, University of Texas;
P. Lundqvist, Stockholm Observatory; and J. C. Wheeler,
University of Texas, communicate:  "High-quality
spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm
and 0.265 nm/pixel) of SN 2002ap was obtained with the ESO Very
Large Telescope UT3 (+ FORS1) on Feb. 3 UT.  A sharp change of the degree
of polarization by more than 1 percent in the wavelength region from
650 nm to 800 nm relative to other wavelength regions is detected. 
The FWHM of the feature is 60.3 nm with centroid at 735.1 nm.
The highest observed degree of polarization is 2.1 percent. 
The polarized feature corresponds to an absorption minimum in the 
flux spectrum.  The polarization of this particular feature
may provide important clues of the structure of the supernova envelope. 
Such large variation across spectral lines is quite
unusual for supernovae, and further spectropolarimetric observations 
are encouraged. "

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have acquired UBVRcIc all-sky photometry for
an 11x11 arcmin field that is approximately centered on
the position of supernovae SN2002ap with the USNOFS 1.0-m telescope
on one photometric night.  Since the supernovae is expected
to brighten further, exposures were short so that no star
in the field is saturated.  We have placed the photometric
data on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sn2002ap.dat
The current photometry has a potential external zero-point
error of less than two percent.  The astrometry in this file
is based on linear plate solutions with respect to USNO-A2.0.
The internal errors are less than 100mas.

As conditions permit, this file will be extended to include
more photometric nights.  M74/NGC628 is a very popular object
to photograph since it is large, bright and beautiful.
A causual search of the public archives for several observatories
indicates that there are dozens of deep plates and CCD images
of the galaxy, many of which will include the supernovae
region.  For example, two such V-band images at NOFS have
approximately the same depth and resolution as the V-band
image indicated by Smartt et al. (GCN 1240
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 ).  A simple
data-mining exercise should give a reasonable time history
of any precursor over several decades.  Towards that end,
we will extend the photometry file down to about V=22 in
the near future.

Stephen Smartt, Enrico Ramirez-Ruiz, Institute of Astronomy,
Cambridge; and Paul Vreeswijk, University of Amsterdam, report:

UBVI images of M74 were taken with the Wide Field Camera on the Isaac
Newton Telescope in July 2001, as part of the INT Wide Field
Survey. At RA=1:36:24.00, DEC=15:45:13.6 (J2000), consistent with the
radio position of SN2002ap (GCN No. 1237) to within 1.3", we detect an
object with B=21.6, V=21.2, I=20.5 (with errors +/- 0.2mag). This is a
fairly faint object in these short (120s) exposures, and the object
shows some inconclusive evidence of being extended. At the spatial
resolution of the images (~50 pc) the object could be an unresolved
small cluster or HII region, or a predominantly bright star on a
variable background. 

Assuming it is a single star, a distance modulus of 29.5 to M74, and
Galactic extinction estimates from Schlegel et al. (1998; E(B-V)=0.07), 
we estimate absolute magnitudes of M_B = -8.2, M_V = -8.5, M_I = -9.1. 
The colours B-V=0.3, V-I=0.6 and absolute magnitudes are consistent
with a very luminous early to mid F-type supergiant. The bolometric
luminosity is approximately 10**5.3 L_solar, which would place the
star in the Luminous Blue Variable region of the HR-diagram (Humphreys
& Davidson 1994, PASP, 704, 1025), and suggest an initial mass of
around 40 M_sol. We currently have no estimate of the internal
reddening in the host galaxy, however note that any significant
extinction would make the star intrinsically bluer and more luminous.
Further astrometry and image shape analysis are required to confirm
that the progenitor object is stellar, and we encourage monitoring of
this very interesting supernova at all wavelengths.

For an image of M74 and BVI zooms of the region around SN2002ap, see:

	http://www.science.uva.nl/~pmv/m74sn2002ap.gif

Taichi Kato (Kyoto U.) write:

   Regarding SN 2002ap (hypernova / GRB ??), VSNET has prepared a special
mailing list dedicated to SN 2002ap event.  This mailing list deals with
most up-to-date information of this supernova.

   Those who wish to subscribe to the list should send an e-mail with a
message line

SUBSCRIBE vsnet-campaign-sn2002ap

   to vsnet-adm@kusastro.kyoto-u.ac.jp

   Also a web page:

   http://www.kusastro.kyoto-u.ac.jp/vsnet/SNe/sn2002ap.html

Regards,
Taichi Kato
VSNET Collaboration

S. R. Kulkarni and E. Berger report on behalf of the Caltech-NRAO-CARA GRB
collaboration:

"The early detection of radio emission from SN 2002ap (GCN 1237
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 ) has a
number of interesting ramifications. Given the distance modulus of M74 of
29.3, the absolute magnitude of the SN is -15.6, and given that the
optical emission is still rising (IAUC 7810) it is safe to assume that we
are seeing the SN before maximum. The optical spectroscopy suggests an age
of 7 days based on analogy with SN 1998bw (IAUC 7811). Adopting this age
and a typical expansion speed of 30,000 km/s the inferred brightness
temperature in the 8.5 GHz band is 3x10^10 K using the 0.4 mJy detection
of Berger, Kulkarni and Frail (GCN 1237
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 ). As in the case of SN 1998bw,
such a high brightness temperature argues for mildly relativistic
expansion (see Kulkarni et al. 1998, Nature, 395, 663). If so, we should
expect strong X-ray emission from inverse Compton scattering of the
optical SN photons as well as measurable angular diameter of 0.2
milliarcsecond, both of which are verifiable with Chandra and VLBA
observations.  In addition to these observations, high frequency (sub-mm
and mm) observations are also required to find the synchrotron self
absorption frequency, which is essential for calculating the energy in the
relativistic blastwave (see Kulkarni et al.  1998, Nature, 395, 663).
Finally, it would be worthwhile inspecting archival data from gamma-ray
burst monitors from the past two weeks to search for a faint GRB in the
same position."

This message may be cited.

E. Berger, S. R. Kulkarni, and D. A. Frail report on behalf of the
Caltech-NRAO-CARA GRB collaboration:

"On 2002, February 1.03 UT we used the VLA at 8.46 GHz to observe the
position of the peculiar Type Ib/c SN2002ap in M74 (IAUC 7810 and 7811).
We detect a radio source with a flux density of 375+/-30 microJy within 1"
of the optical position of this supernova at coordinates (J2000):
RA=01:36:23.920, DEC=15:45:12.867, with an uncertainty of approximately 10
milliarcsec in both coordinates. The optical spectrum of this SN is
similar to that of SN1998bw, and there is some evidence that SN2002ap is a
younger and/or more energetic version of SN1998bw (IAUC 7810).  In view of
the peculiar properties of this object, the radio detection, and the
possible connection of SN 1998bw with GRB 980425, we urge further
observations at all wavelengths."

This message may be cited.