About 100 millisecond (ms) pulsars have been identified in the Galaxy, and only ~10% of them are solitary, i.e. without a binary companion. Nothing is known on the optical emission properties of ...millisecond pulsars. Observations of solitary millisecond pulsars are the only way to detect their faint optical radiation, otherwise buried by the brighter white dwarf companion. As in the case of solitary, non millisecond pulsars, an X-ray detection represents the first step for a follow-up identification campaign in the optical. Among the X-ray detected millisecond pulsars, PSR J2124-3358 stands out as an ideal case because it is very close (<270 pc) and little absorbed. Here, we report on recent VLT observations of the PSR J2124-3358 aimed at the identification of its optical counterpart. No optical emission from the pulsar has been detected down to a limiting flux of V ~ 27.8.
We had reported in Chaty, Mignani, Israel (2002) on the near-infrared (NIR) identification of a possible counterpart to the black hole candidate XTE J1908+094 obtained with the ESO/NTT. Here, we ...present new, follow-up, CFHT adaptive optics observations of the XTE J1908+094 field, which resolved the previously proposed counterpart in two objects separated by about 0.8". Assuming that both objects are potential candidate counterparts, we derive that the binary system is a low-mass system with a companion star which could be either an intermediate/late type (A-K) main sequence star at a distance of 3-10 kpc, or a late-type (\(>\)K) main sequence star at a distance of 1-3 kpc. However, we show that the brighter of the two objects (J ~ 20.1, H ~ 18.7, K' ~ 17.8) is more likely to be the real counterpart of the X-ray source. Its position is more compatible with our astrometric solution, and colours and magnitudes of the other object are not consistent with the lower limit of 3 kpc derived independently from the peak bolometric flux of XTE J1908+094. Further multi-wavelength observations of both candidate counterparts are crucial in order to solve the pending identification.
The state of the art of optical studies of Isolated Neutron Stars (INSs) and
their Pulsar Wind Nebulae (PWNe) is reviewed. In addition, results obtained
from recent HST and VLT observations are ...presented and discussed.
Astrophys.J. 582 (2003) 978-983 We present the results of first deep optical observations of the field of the
old ($\sim 10^8$ yr), nearby, isolated pulsar J0108-1431, in an attempt to
detect its ...optical counterpart. The observations were performed using the FORS1
instrument at the focus of the European Southern Observatory Antu Telescope of
the VLT. Observations with the Australia Telescope Compact Array (ATCA) were
made to determine an accurate position for the radio pulsar at the current
epoch. The imaging data, obtained in the V, B, and U passbands reveal no
counterpart at the revised radio position down to $V \simeq 28$, $B\simeq 28.6$
and $U \simeq 26.4$. For a distance of 130 pc, estimated from the pulsar's
dispersion measure, our constraints on the optical flux put an upper limit of
$T=4.5\times 10^4$ K for the surface temperature of the neutron star, assuming
a stellar radius $R_\infty=13$ km. Our new radio position allows us to place an
upper limit on the pulsar proper motion of 82 mas yr$^{-1}$ which, for d=130
pc, implies a transverse velocity $\la 50$ km sec$^{-1}$.
We have used a set of archived HST/WFPC2 exposures of the inner regions of
the Crab Nebula to obtain a new measurement of the pulsar proper motion, the
first after the original work of Wyckoff & ...Murray, more than 20 years ago. Our
measurement of the pulsar displacement, mu = 18 +/- 3 mas/yr, agrees well with
the value obtained previously. This is noteworthy, since the data we have used
span less than 2 years, as opposed to the 77 years required in the previous
work. With a position angle of 292 +/- 10 deg, the proper motion vector appears
aligned with the axis of symmetry of the inner Crab nebula, as defined by the
direction of the X-ray jet observed by ROSAT. Indeed, if the neutron star
rotation is to be held responsible both for the X-ray jet and for the observed
symmetry, the Crab could provide an example of alignment between spin axis and
proper motion.
The state of the art of optical studies of Isolated Neutron Stars (INSs) and their Pulsar Wind Nebulae (PWNe) is reviewed. In addition, results obtained from recent HST and VLT observations are ...presented and discussed.
We have used a set of archived HST/WFPC2 exposures of the inner regions of the Crab Nebula to obtain a new measurement of the pulsar proper motion, the first after the original work of Wyckoff & ...Murray, more than 20 years ago. Our measurement of the pulsar displacement, mu = 18 +/- 3 mas/yr, agrees well with the value obtained previously. This is noteworthy, since the data we have used span less than 2 years, as opposed to the 77 years required in the previous work. With a position angle of 292 +/- 10 deg, the proper motion vector appears aligned with the axis of symmetry of the inner Crab nebula, as defined by the direction of the X-ray jet observed by ROSAT. Indeed, if the neutron star rotation is to be held responsible both for the X-ray jet and for the observed symmetry, the Crab could provide an example of alignment between spin axis and proper motion.
Astrophys.J. 580 (2002) L147-L150 We report on the proper motion measurement of the proposed optical
counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with
the HST/STIS ...(average epoch 2001.73) we computed a yearly displacement of +97
+/- 1 mas yr^{-1} in RA and +46 +/- 1 mas yr^{-1} in Dec since the epoch
(1994.52) of the original HST/FOC detection. Both the magnitude and direction
of the optical proper motion components are found to be fully consistent with
the most recent VLBA radio measurements. This result provides an unambiguous
confirmation of the pulsar optical identification. In addition, we have used
the combined STIS/FOC datasets to derive information on the pulsar spectrum,
which seems characterized by a power law component, apparently unrelated to the
X-ray emission.
We present the results of first deep optical observations of the field of the old (\(\sim 10^8\) yr), nearby, isolated pulsar J0108-1431, in an attempt to detect its optical counterpart. The ...observations were performed using the FORS1 instrument at the focus of the European Southern Observatory Antu Telescope of the VLT. Observations with the Australia Telescope Compact Array (ATCA) were made to determine an accurate position for the radio pulsar at the current epoch. The imaging data, obtained in the V, B, and U passbands reveal no counterpart at the revised radio position down to \(V \simeq 28\), \(B\simeq 28.6\) and \(U \simeq 26.4\). For a distance of 130 pc, estimated from the pulsar's dispersion measure, our constraints on the optical flux put an upper limit of \(T=4.5\times 10^4\) K for the surface temperature of the neutron star, assuming a stellar radius \(R_\infty=13\) km. Our new radio position allows us to place an upper limit on the pulsar proper motion of 82 mas yr\(^{-1}\) which, for d=130 pc, implies a transverse velocity \(\la 50\) km sec\(^{-1}\).
